Aftermarket cooler

Hey guys, I have an 2005 v6 trd off road tacoma. 208kmiles.
I haul a bassboat (aluminum) and I'd like to upgrade the factory transmission cooler.
Last fall I had to have the transmission and cooler replaced and after that hefty bill, I don't want that problem again.
I have the head mechanic at the toyota garage at my disposal (he has his own garage on the side) for the install, so I'm looking for recommendations at the latest and greatest coolers. I'd like to stay under $200 for parts I'd say, as he said its gonna take him an hour or so to do the job.
Also, is there anything else that is recommended for what I'm doing? Are temp gauges essential?
Thank you in advance!

 

Suggest you ask the “head mechanic “, seems his knowledge and experience would provide the best answer