Another vote for Concentric Mounts. I have both the regular one and one that includes an AirTag
+1. I have 5 Sheehy Labs mounts on 5 different bikes. They are excellent.
Which did you end up with - im researching exactly this now
Just throwing in that I got a seat rail mount of AliExpress for my TCR, there is room for my tool roll in there. I paid 99p for my first one and £1.99 for a second.
I can recomend seatpost mounts from Concentric and saddle mounts from this maker on Etsy. Both are very secure and reliable
I can also recommend Neat Components. I have mounts for a Giant Propel proprietary seatpost and a Cannondale Topstone with round seatpost. I’ve never had an issue.
I eventually bought a 3D printed one from that Etsy account: https://www.etsy.com/shop/LayerFormShop
Nothing extra fancy but it is light, sturdy, does the job. I like it! I am attaching a couple of pictures. Looking at the page (I had to remember of the name) there is a 10% discount code if anyone is interested: THNKU
I use this one and really like how it tucks away behind my mini saddle bag. Only works with Specialized and Trek saddles. https://www.etsy.com/listing/1738713154/garmin-varia-mount-for-trek-blendr?gpla=1&gao=1&&utm_source=bing&utm_medium=cpc&utm_campaign=shopping_us_en_us_ds_med-toys_and_games&utm_custom1=_k_9d6c6c34ae031ffc1dda068762a3812e_k_&utm_content=bing_412365361_1299623041639860_81226503736773_pla-4584826055760436:pla-4584826055760436_m__1738713154&utm_custom2=412365361&msclkid=9d6c6c34ae031ffc1dda068762a3812e