yet another newbie with a honda trx 300 fw

Hello there! Now when I say newbie, I really mean newbie. However, I’m like a sponge and welcome any and all knowledge. So here’s my problem…one day in sunny central Oregon the boyfriend and I decided to go shed hunting. He loaded the 4 Wheeler up on the trailer, hooked on and off we were. While doing 55mph on the hwy we heard a weird noise, and in the rear view mirror saw the trailer speeding away with my 4 Wheeler strapped on it. Long story short, it did a few flips before slamming into a ditch thanks to the boyfriend who forgot to lock the hitch to the ball:( after nursing her back to health for a few weeks, I am down to one thing to have her complete and up and running again..the rear final drive. I ordered and received a differential housing unit only to find out that honda no longer makes the case cover…. please help!!!!!! Is there there any way around this without having to order the whole differential for an additional $600? I know 88-00 works for my 94, but I’m not having any luck finding this only piece I need!!! Thank you all for listening to me wine:)