that's an awful big box for such a simple teeny tiny circuit. I took the schematic and made a very nice compact small perf board layout. I could build one of these into a 1590a enclosure. small enough that it would be thinner than your average guitar strap. and lighter too. You could even get it so that it has a mogami cable coming out of it and a clip on the enclosure- so you could just plug it in and have a short cable going strat to your guitar clip it on your strap and plug the other end into your pedalboard or amp or whatever. having the cable built in would eliminate another jack and another place to lose signal quality removed.
If you're interested I could share my layout for the circuit. If not PM me!