But in all seriousness, there is somewhat of a guarantee when finding a host nem for percs -- as others mentioned -- get their natural host anemone and they'll be in it quicker than you can complain about how many times people ask about a host nem for a perc.
To reiterate, the three host species are:
1. Stichodactyla gigantea (aka true carpet anemone, "gig" for short, not "gigas" which can be confused with a Tridacna)
2. Heteractis magnifica (aka ritteri or magnificent anemone, "mag" for short)
3. Stichodactyla mertensii (aka merten's anemone or "mertensii" for short)
All three (unless a very small one is found, which is extremely rare but not impossible to find) require a large tank. Once acclimated, all three will thrive in the proper environment. Each has its own environmental likes, and each has its own quirks (for example, mags roam around A LOT if they aren't happy) so definitely do some research prior to purchasing.
And yes.. we're here to help!