HOMB 175 amp main Breaker

[Russ1]

We can not track down a HOMB 175 amp main breaker.  All the one's out there are HOMA 175 amp main breaker.  The electrical panel says only the HOMB breakers are acceptable for the main breaker.  Both breakers are the same style and size.  Can you use the HOMA in this case and not void the UL listing of the main electrical panel?  The AHJ is requesting a cover letter from the manufacture that this is acceptable.  I can't track anyone down to get this cover letter showing approval from the manufacture.