Check out k19/k29/k39/k55/k66, all below or around rm200

Skyreach 4 mini
https://nfc-systems.com/skyreach-4-mini

Velka 3
https://www.velkase.com/products/velka-3

These are the 2 smallest I can think off that uses flex

try to look for SGPC K39

it is somewhat similar to the Velka 3

Any b450 owner here? Contemplating whether will be the B550 worth waiting since price is almost twice of B450.
Only Benefit of going B550 that I see
1) PCIE4.0-Not much diff since not having a PCIE4 Nvme ssd
2) Extra M2 Nvme Slot - I do have a 1x512GB and 1x 1TB Nvme but 1TB shud be sufficient for me since I only play Destiny and Apex Legends.
3) Wifi 6 - This would need some input from B450I owner whether you guys have tried upgrading the wifi card to Intel AX200, i already have this card so it should be a simple swap for the upgrade.
4) Overclocking - Not really ocing but rather more on undervolting to keep temps in check for me.
5) Extra Fan Header - no room for additional case fans in my build so non-issue

So, really hard for me to justify the roughly estimated 300-400 extra for B550 :/
Source:WCCFTECh

Regarding the wifi upgrade do you have plans to upgrade it or keeping it at ac is good for you?