My husband has 13 x 7 Superlites. At the moment they have the Dunlop 195/45/13's on them. He only just had them put on the car last weekend. He says they are fine. You will find though that they are hard to find here in Oz. Only places I know that have them are Stuckey's Tyres in Brunswick, Melbourne. Sell them for about $230 each. I think he is the only person that Dunlop let import of this size tyre in Oz. Also at Northern Mini Parts he imports them direct from UK. He just buys them and then brings them back in his container. Think they are a little cheaper there.
Continental do have this size also. Take a look at
http://www.conti-online.com/generator/www/de/en/continental/automobile/themes/pc_tyres/summer/conti_sport_contact/dimension_en.html
I have Continental 195/40/14's on my Mini and I find them great. Think the Continental would probably be a lot cheaper too. Try this email address for them. This guy was fantastic when I bought mine. Very helpful. He is located in Sydney but he had mine sent to Melbourne for me at a very reasonable price.
[email protected].
Also Simes (not sure of spelling) make a 175/?/13 which people are using on the 13 x 7's but most reports I have heard aren't very good.
Wouldn't go any winder than a 195 because I think you will find they will scrape a lot. We have our guards cut and the 195 on the 13 x 7's still scrape in certain circumstances.
Good luck and hope this helps.