New experience.

On grindr

Well you're here
Other than that depends on where you're located. There are plenty of online portals, apps and small ads sites that would offer that. You can try special clubs or bars, or bi/ gay sauna.
What I don't get is, why they have to be straight? If a guy is really straight, he won't give you a BJ or anything else.
I'd imagine, if U go into a Bi or gay club or sauna and tell you're straight and wanna try something 1st time, you will have more than enough willing guys to help you out. From what I know, it's a kinda kink for some guys to "have it " with a 1st time straight guy.

Hii

Go to a Porn Kino here in Germany and utilise the gloryhole. Even in the "straight" areas there are usually gay or bi guys

I dint know if many that exist though. It seems more Glory holes would be operational with the current virus situation.