Hiring an interpreter for site tour

My friend and I are visiting Japan in May and were planning on taking a tour of the Kasukabe Underground Flood Protection Tank. I've read that if you are a foreigner, you must either speak Japanese reasonably well or bring someone who can interpret for you as the tour is in Japanese and in the event of an Emergency you will need to understand the Emergency instructions. My Japanese is probably not strong enough for that and as such we were looking at hiring an interpreter to come on the tour with us. I was hoping someone on the forum might have some advice on how we might go about this or where we can start looking.