Is there any way to find out what kind or where to get the correst thermal coupler for my Berkeley sr 1001?

These heaters are all pretty contankerous and I doubt the thermocouple has failed, unless something has been done to it (I've got two of these heaters, and have to work on them all the time. Have never replaced a t-couple.). I usually find the problem with the t-couple is insufficient pilot flame.
Problems fall into two areas -
1) Bugs building nests or spiders building webs in the pilot hood and main burner. Disassemble the top head and clean everything. While you have the pilot tubing disconnected, be sure to blow out the tube (by mouth), making sure you have flow. Also make sure you clear the air mix chamber in the base of the pilot hood.
2) The regulator in the bottom of the unit begins to stiffen up after 3-5 years of operation. I have found universal replacement regulators at the local Lowe's and Home Depot.
Make sure all t-couple connections are snug tight.

Let me know what you find.