Actually, 谷 飛 龍 (Bruce), in Korean, your name is just sounded out if you want to spell it in 한글. Same with company names (월마트 = Walmart), some borrowed English words (화이팅! = fighting!), things like that.
I'm 사라, 새라, or 세라, haha. I've seen it spelt all three ways.
Anyway, "리자" is probably the closest spelling for "Riza". I think "리저" might also work. I'm not positive though. I hope a native speaker answers your question, haha. ^^