Box to return Tacx Neo bike smart

I received my new Tacx Neo bike smart on 29/12/23 and by 05/01/24 it stopped working properly and Garmin have agreed return. I was going to return through the supplier but they need it boxed and I no longer have a box due to lack of storage space. I therefore went through Garmin warranty but now they also need it boxed.

has anyone else had this issue and recommend a box in the uk that is suitable for the weight. although I don’t think I should need to provide a box myself for a faulty product when I have already spent £2000.

any ideas?