I have no experience with Ikonta, other than a lust for one... but most lenses of that description use push-on filters. One way is to use Kodak series filters (series number indicates the size, Google the Wikipedia "filters"). You'd meaure the outside of your lens, buy a series adapters in that size, and then the filters/hood goes into that. The filters have no threads but sit in the adapter and are held in with either a retaining ring or a hood. Series adapters, filters, and hoods are still fairly easily available on ebay.