There is only one commercial RC hydrofoil kit, and it is out of production.
It may have been the one you had so many years ago.
It was the
Gunze Sangyo PT-50.
It can still be found on e-bay, typically out of Korea, but it also usually sells for $380-559 on auction.
There is one other person that advertises a very nice looking RHS-200 hull/kit, but doesn't say anything about the price. I have tried contacting him twice, and perhaps it is a language barrier, but I got less than satisfactory responses from him. Everything about the website says it's for sale, but nothing on how to obtain one.
http://www.modelboatmayhem.co.uk/scalespeed/rhs_en.htm
If you have any luck or decide to try ordering one let me know, as this is a gorgeous kit, and probably a quicker build than scratchbuilding my own(as I have been trying to do)