You can get drive cages that can be mounted in most machines from Evercase. They are the same ones that fit most of the 42x2 (4252, 4292, etc.) series. You just need to drill two holes to mount their bases (might even be able to use industrial mounting tape). They have optional rubber drive isolators too, so don't forget to order a set of those with each cage you buy.
. Chenbro also has add-on cages for some of their cases but I don't know if they are as generically useful as the ones from Evercase.
.bh.