Well, that depends. What specific problems are you having? FSR makes a lot of different floor boxes, as do some other manufacturers, so what model are your
current boxes? There are differences in not only overall size but also in
stage/raised floor mount versus slab mount, plate quantity and size, depth, blank/pre-punched or filled inserts, knockouts and so on. So like many other things, what is 'comparable' takes knowing a
bit more about what you have and the specific requirements that would define something as being comparable.
The first boxes that come to mind for
stage use are FSR, Ace Backstage and Mystery Electronics. There are also some floor boxes from companies better known in the electrical world such as Hubble and Walker. And there are some other companies that make some special application products. But it is difficult to say who makes something that might specifically meet your requirements without those requirements being better defined.