Rota Wheels in the Philipenes had 13's in their catalog but not for about a year and a half, has now done short runs of 13x7 alloy wheels ....look a like Panasports.
I got four 4 0n 4.5" bc recently . Very nice wheels. 12.5 pounds and a pound might be able to be
trimmed off. Contact Troy Ermish in the San Fran CA area. He brought in 4.5" , and other bolt
circles in 13. Back spacing on the 4.5' was 4.125". They came out to about $550 a set/4.
BTW.....I have a set of Real Wheels for sale. 4 on 4.5" ...2 7"s and 2 8's 3 7/8" back spacing. Polished alum and nice. $450/set.
PM if interested.