WD !TB M2 SN750 with heatsink - fitting probs

Due to upgrades I have ended up with a spare ITB SN750 with factory heatsink. My motherboards two M2 slots are occupied. I want to buy an external USB caddy or a PCIe adapter board that will be able to fit the SSD with its heatsink attached.
Not realising there would be a problem I bought a generic caddy but found I could not mate the M2 connectors because the underplate of the heatsink raises the M2 connector on the SSD too high.
I have read that it is not advisable to try to remove the SSD heatsink.
Has anyone else encountered and solved this problem? Can anyone recommend a caddy or PCIe card that they know will fit the SSD with its heatsink intact? Thanks to anyone who can advise on this.