Advice mounting Noctua fan duct onto a clipped fan?

I'm making an SFF build with a Fromd T1 and I made a mistake and got the Noctua fam duct foams (NA-FD1) thinking I'd be able to install them, but they require you to use the provided screws, to then put a tube on them and then insert the foam.

The problem is my cpu cooler is an AXP90-X47 and the fan is mounted using 2 metal clips, and the heatsink has no threaded holes to put screws through, so there's no obvious way to install the foam. I've added some pics (I'll trim the plastic tubes shorter later).

Does anyone have any good ideas on how to solve this without just using tape? 🤣