I have a perfume on plus the active event and still cant find one

Finding a LG themed works the same way as fest themed, except they're a lot rarer. Sylesties, in general, are rarer in the LG (as compared to other zones), but luckily the LG perfume only counts pet encounters so it'll last a while. Just keep grinding and hope rng favors you. As with the fest perfume, if you don't find any themed with a perfume, the chances of finding a themed with the next perfume increases significantly.

As Tigress said, they're a lot rarer than fest zone pets- way, way, way rarer. Due to the combo of pets having a lower encounter rate in general, the Grove being available at all times of the year, and the Grove themes getting the bonus of the bonus stats...

well, a theme in a fest zone lets say is maybe a 1/1000 chance? fight about 1000 enemies, and you'll probably find one theme. LG themes tend to put that to absolute shame, and are usually more like... tens of thousands to one (or it sure feels like it.) In all the time the grove has existed (though I'm not as active about grove-wandering as I could be and I don't use grove perfumes) I've encountered 12 Grove themes and found 6 theme eggs (though I am not a mass-releaser) Keeps their value up, at least.

Just gotta be persistent and hope RNG rolls in your favour