The rather serious implications are that it appears that your steering column and steering wheel boss are, if not unique, then pretty rare, so in effect you are stuck with what you have, unless you do indeed, as you suggested previously, replace your entire steering column.
However, since the top end is different to the norm, it's possible that bottom end might be also, so there has to be a chance you would need to change the steering box and linkages etc at the bottom end as well.....
Now this is of course speculation, since we can't be sure until you try, but logically it has to be a possibility. So the key question is, how much do you want to change your existing steering wheel?
There could be other options. For example, on my Reliant the steering wheel boss fits onto a hex spigot. I can't recall the exact dimensions, but I'd guess it's about 15-17mm across the points. It's possible you could get a local machine shop to grind your circular splined spigot to a hexagonal one, and then you could fit Momo or Mountney etc. But that's a huge amount of work, and won't be cheap.
Final thought: Demon Tweeks do a large range of bosses and special fittings like quick-release etc - might be worth giving them a call to see if they know anything about a 37-spline fitting.
Also might be worth a chat with Piotr (user name Piotross) to see if the spec you have was unique to Polish production, for example.
