They weren't really "shocks", more like seat springs. Folks here have used the Northern Tool 12" shocks to good effect, but you have to make a 1" extension to get the proper seat height, either a new seat shock mount that is 1" longer (easiest) or some kind of extension for the lower shock mount. That is probably the cheapest, option. Treatland.tv sells 340mm (roughly >13") shocks that are the proper length, but I am not sure if they actually have damping or if they are springs only. If you want to check out Ebay, look for Puch moped shocks, they should be the proper length (my FreeSpirit moped's shocks are the correct length and have no damping, the FS moped is essentially a re-badged Puch that Sears sold waaaaayyyyy back in the late '70's). New from Treatland is probably the most expensive option, but no modding would be required, used Puch shocks could be the cheapest solution, but you take a chance on condition.
Paul