I have an
extensive collection of MFM/RLL drives and have _never_ run
 across one with that interface in a 3.5" form-factor.  Not sure that
 anything of this sort existed.  5.25" 1/2-ht. was about as
 sophisticated as they got. 
 I've got quite a few Rodime ones here - can't remember the model number
 without going and digging them out, I'm afraid. I *think* they're 30MB. 
 
I've owned a 40MB one for years.  I would like to upgrade the machine.
It's a IBM PS/2 Model 50, and it's my favorite PC.  Period.
Peace...  Sridhar