Where I can go to purchase the transmission pawl

If you are referring to the parking pawl, that is not the type of part an auto parts store would stock. You can find a good used one at any transmission specialty shop or you can order it through the dealer's parts department. You can also get one at a salvage yard, but they are not going to disassemble a good transmission. They will have broken transmissions from crashed vehicles. Those go for scrap metal or are sold to re-builders. Be aware if they have to pay an employee to take the part out, they will have to charge you more for it.

That will not be something that the average corner parts store will have. From looking it is a part that is no longer made. I would call a couple transmission shops and see if they can get a replacement, they usually have a few donor transmissions for the odd parts.
Or if yours is broken or worn you might be able to have it welded up or even have one made at a machine shop.