I bought a '95 GS500E last spring, but it had no owner's manual.  After trying to get the manual through a Suzuki dealer for six months, Suzuki says it is unavailable now and forevermore.   I did purchase a Repair Manual through this site, but it does not answer some basic questions for me such as how big is the gas tank, etc...  I do not believe a '95 gas tank  is 5.3 gals as listed on the specs page here.

Does anyone know of another source for a manual?

Welcome!  
Since the bike hasn't changed much over the years, have you try asking the dealership for a manual from another year? They also had a problem ordering a manual for me for the exact year I wanted.
My bike's an '89 but the manual I ended up with is not...

Well, the gas tank on the newest models is a gallon bigger (so yours is 4.3 gal), seat is different, carbs are changed (New ones have 3 jets, yours has 2)

The bike really hasn't changed much over the years.  So no worry

I just got my official Suzuki service manual.  At a glance, not too much new stuff that you can't get from Clymers/Haynes, but I do like all the torque specs in one place and how cables/hoses should be routed

I didn't know I could lock a helmet to the bike until I came here    .  It wasn't mentioned in the Haynes manual.  So I can kinda see the value of a MOM.  I suppose now that the 500F is coming, the dealer will be able to get those manuals just fine.