They go into heat about once a month, although unless you know your female(s) VERY well, it's very difficult to tell when it happens. No, you should not have that many males in a cage with one female, whether or not the males are neutered. It's not a good idea to have that many males in a cage with one female. Colonies work better when there are more females than males, or when there is an equal number of males to females. There is a good chance the males would fight over her. Also, look at this from the female's perspective. Is she really supposed to satisfy the urges of 4-5 males? That's not cool. Because neutering gliders doesn't mean they don't have sex. Males will still be interested in sex, they just won't be able to produce offspring.
DISCLAIMER: I only have female gliders (two of them). I did a lot of research when I got my second girl. I wasn't sure if I should get just one glider, an established pair, a male, a female, or what when I was trying to find Luna a companion(s). So everything I've just said is based on research that I've done, not personal experience with larger, mostly male colonies.
I know the user here viciousencounters makes cage sets. She has an Etsy site, or you can likely PM her about it. I've bought from her before, as have others on GG. She isn't the only one, many other users here make toys/pouches/cage accessories. Google can easily turn up loads of vendors. Cage set sizes vary based on the size of the cage and the amount of gliders the cage set is intended for. Many vendors have set sizes/prices for cage sets, and many (viciousencounters will do this, I know) will happily custom make you a cage set if you speak with them about it.