The best of course would be to train in Japan. There are three dōjōs, one in Nara, one in Higashiōsaka and one in Nagoya, where training is held regularly. Addresses, training hours and contact data can be found at the Japanese site of the Hōzōinryū.
Outside Japan the only place offering Hôzôinryû Takadaha Sôjutsu training in Europe on a regular base is located in Hamburg/Germany (recently a branch opened in Toronto/Canada as well):
Keikoyari (training spears) are not obtained easily even in Japan. The author saw a kamayari for sale in a budō equipment shop in Tōkyō just once. And there is only one maker/distributor of wooden weapons who sells kamayari and suyari through his webshop. Recently he ships the spears to destinations outside Japan as well, but they are quite expensive.