Portative organs sound beautiful but are *very* expensive, even as a kit.

I have never heard of a portable harpsichord. Clavichords are often portable but they are also almost inaudible. Both harpsichords and clavichords need thorough retuning before every performance, even more so if transported.

Vibraphones are enormous, as hard to transport as an upright piano.

Celestas are also far too big. A reduced-size version was the dulcetone, intended as an organ substitute for missionaries in hostile tropical climates. I've played one that had been left in the same room in a rarely-heated cottage in a remote part of the Western Isles of Scotland for about 80 years, and it had no major problems. They sound very nice. I don't think they've been made since WW1, though, and there aren't many around on the second-hand market, unless you want to scour the flea markets in Fiji and Kenya.

The accordion gives you the most power and flexibility for the size, weight and money.