Sorry this doesn't actually help you. But I was looking at idol names that I stumbled into a while back. And there was someone who released in her early 20s a while back and she also released one where she was around 40 or older. It might have been while I was searching hanatane-music.blogspot.com but IDK if there's an easy way to search through there without using someone's name.
If you google グラビア X 嵗 , replace X with the age you're looking for and maybe you'll find something. I put 40 but I'd guess that "old" in the gravure scene would be 35 at most.
Probably your best bet - she started gravure when she was 42 or so and she's 51 now: Yuko Nakagawa 中川祐子
https://www.instagram.com/nakagawa.yuko/
She's 34 and still pushing stuff out: Tono Chika 遠野千夏
https://www.instagram.com/kanayama_chika/ https://twitter.com/tono_chika
Looks like she just does acting now but she's 40+ and still posts daily life content on youtube: Chiharu Niiyama 新山千春
https://www.youtube.com/@chiharoom/videos
I can't find official releases but this person was 50ish when she released whatever's being advertised in this video:
https://twitter.com/chikamarodog
I could find more from googling but I'll leave you to figure out what you're interested in. I don't think you'll find much else at the early 30s age for gravure content because people at that age would've been popular 10 years ago, like Rui Kiriyama as you mentioned. But if you're interested in content besides IVs that age range then reply to this message because I still follow former idols that do youtube or other stuff outside of gravure nowadays.
I'll do you one better, actually. Usaki Yuki did some IVs a few years ago, when she would've been 33 under the name 宇沙木 ゆき. In her youngest years, she went by 鈴木祐紀, and she released a good number under 鈴木ゆき (both pronounced Suzuki Yuki) but that name is confused on google search with some other musician. Ironically, The gravure idol Usaki/Suzuki Yuki is in a rockband nowadays so it gets a bit more confusing. This is her wiki page:
https://ja.wikipedia.org/wiki/宇沙木ゆき