Richard,
The only other option would seem to be the wheels offered by this Japanese company who produce a lightweight alloy replica TZ/Ti Super wheel, with the original strengthening webs that other wheels seem to lack. Price at the moment is $275 per wheel but I cannot tell you much more than that since the entire website is in Japanese. I believe that someone on the BB might be able to help you with this side of things. Let us know what you discover!
http://www.babu.jp/~autoparco/parts/no39.html
Alex.
p.s. I seem to recall a guy in the UK making these wheels too, amongst other racing parts - I think I recognised the name as one of the 750/101 racers over here - but for some reason his website is not on my Favorites list and Google hasn't turned up anything. Maybe someone else knows what I am talking about and can supply the link.