I do not know if the drinking tube is compatible with US canteens with drinking tube cap.  Might, might not.  Also don't know if drinking tube on the mask is compatible with Israeli-made Source bladder fittings, which are identical to CamelBak Hydrolink fittings.  Rather doubt it as the Izzy surplus masks are presumably older than the Source/Hydrolink systems.

Also, no expert, but I believe the proper technique of drinking with a mask on is to invert and elevate the canteen so that the water will flow into the mask's drinking tube.  I don't believe it is easy to pull any sort of suction on the mouthpiece within the mask, as would be done while wearing a bladder.

In short, if the mask's drinking tube fitting fits something common/suitable/available, great.  If not, then it's worthless until you find something that will interface with it. 

Here's the Result of a quick search for gas mask drinking adaptors.  Note the Izzy canteen (($18) hooked up to the same mask via long tube.  Again, I have no idea whether this mask is compatible with gas mask drinking tube adaptors.  Adaptors offered by CamelBak are focused on US masks, like These Adaptors.

The white plug inserted in the receiver for the filter is actually a valuable training aid.  It has a hole in it and is meant to simulate the restriction when wearing a filter.  the oblong filter holder is intended to be stored inside the mask, and so help it keep its shape during storage.

Note that there is no easily available means to insert corrective lenses into the mask.  This mask was intended for civilians who were sheltering-in-place, and not for the front-line military, who were expected to be able to accomplish various tasks, some of which required masks that allowed use of vision-correcting inserts so that the user could see properly.  Modern Izzy military Gas Mask

Given the possible life-saving nature of this device, if wearing it in a toxic gas environment, I would, without question, replace the very old filters that are supplied.  Use up the old filters while painting or in some similar environment.  Be aware that most filters plug up due to dust long before their Chemical filtering capability is exhausted.  IOW, don't buy two new filters and think you have things covered. 

Approved Gas masks (AGM) is a very good site from which to obtain information.  I would shoot them an e-mail about what you might need to hook up an Izzy mask to a cheap US canteen.  Maybe they have some suggestions.   They are pricey, but as against that, they do not sell outdated surplus items.  As for filters and masks, shop around, but make sure that you are buying item(s) that are guaranteed to be GTG when you need them.  

As to filters, My (possibly incorrect) information is that filters stored with original Quick-removal caps/plugs have a fairly decent storage life.  But, that life is finite, and nobody will guarantee such a filter for very long.  "Very Long" is a vague term, when it comes to saving one's life.  Almost all mil surplus filters can safely be considered to be past their prime, else, they would not have been sold-off/discarded.  If buying new filters, I would strongly suggest sealing them, individually, in vacuum sealed bags, and so not relying on the QD caps and plugs.  Once sealed in a vacuum-sealed bag, I (again not an expert) know of nothing that would prevent such sealed filters from really lasting a Very Long Time, as in possibly decades.  You could use your worn-out training filters as experimental models for vac-bag sealing, and also in training in ripping the vac-bag off the thing.

The truth about gas masks is that the user needs sufficient WARNING to don them.  Given that warning, a gas mask will protect you against the inhaled agents for which the filter was designed.  No more, no less, assuming a fresh, GTG filter, a mask that is properly functioning, and as many filters as needed.  How many?  Depends on a lot of things.  Some stated filter lifetimes speak in terms of minutes, but that is probably the lawyers talking--Or, is it?  I dunno.  You might read up on mil manuals about changing filters.  Like ammo, it is probably better to have too many filters than too few. Your call. 

This topic has been discussed, many times, on Survival Discussions Forum, and Survival Gear Forum.  A search on both those forums will be informative.