what are the best available bang for the buck options for a top cover mount? the Zahal 1 is ~300 bux, is it really that much better? can the stock still fold w/the mount?

I like mine, only issue is when you need to take it off for some reason.

Holds zero well enough for my shorties, for the full size rifle I like the side mount better.

where did you buy it from?  they seem to be few and far in between.

I'd get a side-rail from CSA, and a side mount from RS Regulate. Easy to remove from the rifle to clean it, excellent return to zero for your optic.

Got one from Zahal, and a used one from eBay.  Was 4 years ago.

I have a full size VZ2008 with the side rail and RS Regulate mount, it's OK, just heavy and bulky

There are only two good options:

First is Zendl/Gunexpert cover:
http://www.sa58.cz/sa-58/prislusenstvi/kryt-zaveru/#! hands down, the most practical, compact. its reliable and holds zero, also tested and used in Astan by people who helped to create it. Its expensive...
Second:
RR Arms cover that requires no change to original ocver, just one pin replacement. Holds zero, no tools needed to disassmeble, but its bulkier, costs about half the previous one.
https://www.rrarms.cz/customers-outside-of-czech-republic/dust-cover-pro/

I use both of those at my vz.58s, the Zendl one since 2012.. and still not a single issue. That will not help with long scope.

There is also option of full  top rail:
https://www.gundocthor.cz/vz58/cnc-celokryt-pro-vz58
I dnnt have this one, but friend seems to be satisfied with it. But it adds substantial weight to othervise feather-light vz.58.

Zahal is just rebranded screw-held gundocthor/kinggun and (had one shortly for testing before i send it to Texas) and besides price, it has no merit.

There's a company in Canada that makes one. Magwedge is the name, You have to remove the rear sight for it to fit.

https://www.magwedge.com/product/cz-858-tactical-rail/

What stock are you using?

The magnetic rail works great.