I actually need rigid arch support so I don't know of anything specific to recommend. I was using some Bontrager insoles that had a flexible arch insert, but they don't sell them anymore. Instead they seem to be offering something with Superfeet. There's a low arch version and they have a 30-day guarantee so you could try them and return them if they don't work out.
https://www.trekbikes.com/us/en_US/a...?colorCode=red
What kind of insoles were in your shoes when you bought them? Every pair of cycling shoes I've had came with totally flat insoles -- maybe something like that would no arch would work?
Also there is an online store called theinsolestore.com. They might have something.
I sympathize -- finding the right insole is never easy. Since I started having ankle tendon problems I now need the rigid arch support, so I've been trying Sole insoles in my bike shoes. But even the thinnest version is too thick so if I continue to use them I will need to get larger shoes. They also make my feet feel hot and my toes hurt. I'm going to try a new version with a metatarsal pad, but may end up having to look at different brands.
- Gray 2010 carbon WSD road bike, Rivet Independence saddle
- Red hardtail 26" aluminum mountain bike, Bontrager Evoke WSD saddle
- Royal blue 2018 aluminum gravel bike, Rivet Pearl saddle
Gone but not forgotten:
- Silver 2003 aluminum road bike
- Two awesome worn out Juliana saddles