Custom thumbrest?

[Rich]

I have a very lovely [url="http://www.brightonguitars.co.uk/image/cache/data/products/tanglewood/TGRB-CE-700x700.jpg"]Tanglewood acoustic bass guitar[/url], but I find it a bit challenging to play as there's nowhere to anchor my thumb. I'd like to get hold of a small, discrete thumbrest but searches for such an item are coming to nought. The sort of thing I have in mind is as per Jonas Hellborg's Wechter (see pic below), but made of rosewood to match the back/sides/f'board of my bass. As I said, the smaller the better really, no more than about an inch long. The idea would be to attach with double-sided carpet tape or the like, rather than screw or glue.
Does anyone know of such an item available anywhere, or failing that of a UK luthier who would be able/willing to knock up something suitable for a reasonable cost? Doesn't have to be local, just a good artisan who won't take 6 months to deliver.