Hi Pamela. Yep, just ask them! Before you do that though, have in mind what you are willing to accept, AND what you can offer the gym to make this a true ‘win-win’ for you and them. That will give you a better chance of success in finding a place.
What I mean by what you can offer is something like: do you have specialized skills or knowledge that the particular gym does not already have in-house? If yes, then I would accentuate that in approaching them. This might not only allow you to gain entry into the gym for your own clients, but you may find them referring some of their clients to you as well.
I hope that this helps.