I read a lot about jackets a few months ago when I wanted to replace my Icon textile jacket. Ended up going with a Joe Rocket Sonic 2.0. Expensive piece, but great protection. Not as good as a textile for warmer weather, but the protection is worth it. Might look at a HiViz jacket for the Grom.
i have 2 joe rocket jackets.. one is mesh that i use during the summer.. the other is a Honda branded textile jacket that has a zip out winter liner.. it has been a great jacket.. rode it in the smokies during fall when it rained the whole day and it did great.. my hands were freezing but i was nice and warm.. a few years after i bought it the zipper messed up.. i thought "fuck there goes my jacket" but I emailed joe rocket and the lady emailed back and said what is the model on the zipper.. i didnt even know there was one but i looked and sure enough some numbers.. emailed her back.. within 2 days i had 2 new zippers and instructions on how to install it.. she emailed me back to confirm i received the zippers and if i needed help installing.. i mean that was over 2yrs after i got the jacket.. that is great customer service and turnaround.. i love mine..
Since Teknic is going out of business all their gear on RevZilla is crazy discounted. I just bought their Striker textile jacket, a $250 jacket, for $89 last night. Hope it fits! (If not I could probably craigslist it for more than I bought it for.) It's 3 season, which in central Texas should mean year round.