I'd just use the aquarium sealant to keep liquids(such as urine)from leaking out,but use some sort of screws to attach the acrylic
I don't think there would be any good solution other than that though.
This is the only positive side to glass as silicon based sealant(aka aquarium sealant)works just fine with glass.However acrylic has advantages over glass especially as far as safety features go,since it doesn't shatter and it would take very extreme methods to break acrylic,so it is just a minor problem to work around(plus it's much lighter)!