Andrew,
This may prove to be a useful learning situation. The tormek website (history tab) lists your SVD-185 as beginning in 1996. That is a twenty year production run, at least for the main jig. You are not the first Tormeker to use a small gouge. Granted the new jig has corrected the problem for a price. What did turners do for the last twenty years?
I suggest you contact Tormek support. Send them an email at support@tormek.se I suspect they may have received the same question numerous times, especially with mini lathe tools becoming popular. Please post their response. Tell them that purchasing the 186 is not an option at this time.
As an experiment, you might try several thicknesses of a cut up business card or cereal box.
Another alternative would be to teach yourself to sharpen the small gouge freehand. This may not be as tedious as you might think. With sharpening (as opposed to shaping) a small gouge, very little steel is actually removed. Set your gouge directly on the universal support bar. Work slowly and carefully with a very light touch. Consider grading your grinding wheel fine. I suspect you will be pleasantly surprised in a very few minutes with a sharp gouge and no out of pocket expense. My grandfather sharpened his lathe tools this way and made very nice chairs.
Why didn't I put this in the first post? To be perfectly honest, it didn't occur to me. Like you, I am a creature of the buy another tool to fix the problem mindset. That is not a good mindset! You should try sharpening your gouge handheld.
Keep us posted!
Ken