I suggest you reconsider your position on bladder carriers with separate shoulder straps.  When you stop to re-fill your attached bladder, you will need to remove your entire rig; this soon becomes a PITA, and according to Murphy's Law, when your rig is lying at your feet will be the exact time when you will need to be wearing it.  Not every time, of course, but when the crisis happens.  That's Murphy's Law.

In addition to this, attached bladders can be problematic when seated in vehicles.  So can bladders with shoulder straps, but the latter can be doffed, whereas the former not without doffing the entire rig, which is when Mr. Murphy appears.

If you elect to go attached, the suggestions above are good ones.  The unreferenced short TT FightLight harness has NO provision for securing any sort of bladder on the backside, although is has sewn-in straps on the front which can be used for such a purpose.  The M-1967 has metal snap buckles on the rear of the harness, and these can be very problematic when attempting to wear any sort of backpack over them.  Fine otherwise, but why limit one's options, unnecessarily?  I would suggest some sort of harness that was so constructed to allow minimum body coverage, as rigs of this type are typically worn in warmer climates where max body cooling is an asset.

In truth, any set of suspenders/harness that has an unused set of "D" rings or even a sewn strap on the front of the shoulder straps could be configured to attach a MOLLE-PALS bladder carrier of any size with some strapping and some tri-glide buckles.  Getting fancy, some QD buckles, some tri-glide buckles, and you have a detachable bladder carrier without shoulder straps.  If it's a bladder carrier carrying 100+ oz, then you'll need a belly band with QD buckle.  That can be woven-in to the pre-existing MOLLE/PALS attachment straps on the bladder carrier.

If you want a low cost set of 4-point suspenders, then go Here.  Now, assuming you want to attach a bladder carrier, then run one each tri-glide buckle up the front straps until they run up against the wider shoulder webbing.  You have now created secure anchor points for the straps that will attach the upper portions of your bladder carrier.  Like a "D" ring, only different.  You'll still need a belly band, secured with an adjustable QD buckle, to secure the lower portion of the bladder carrier.  Don't worry about stupid low price.  ATS is GTG, and I have a few of these suspenders.

I have done this exact thing, experimenting with attached bladder carriers, bladder carriers attached with QD buckles, and independent (with integral shoulder straps) bladder carriers.  I have come to think that the latter is much less hassle overall, as long as the shoulder straps have an sternum strap, which is essential.  Don't leave home without it.  
  
Your call, of course.