Car model:Toyota Corona

Engine type:22RE

Problem: RT142 (IRS) need a new diff gasket. I have tried re-sealing with gasket goo, only held up a week. I have tried everywhere to find a "new" one.

I believe my problem is that the diff was used in other later model toyotas, and there would be a part number somewhere for the other models.

Short of making my own gasket, any links, helps, tips, suppliers?

Thankyou in advance.