Brief update: After a fair bit of research, I've sourced some Velocity Cliffhanger rims and will pair to Bitex 103 touring hubs. These hubs get decent reviews and a couple of good YouTube videos. I also looked at Shimano Deore T610 and M610 hubs (no longer made, but can be found with a lot of searching), but the Bitex were a step up, and not horrendously spendy.
I ended up only being able to get the disc brake Cliffhanger rims, but as mentioned here and in a couple of other threads, these can be used with rim brakes. I did notice the join on the rim wasn't especially smooth, so might need to sand down a bit.
Another option that I found was Kinlin XM-25, but these rims are a bit narrower (21 mm internal width) compared to the Cliffhangers (25 mm internal width) and so probably not best suited to the wider tyres I'm using. The Kinlin rims were a fair bit lighter, so would be more suited to anyone looking for something similar, but for narrower touring tyres.
I'll post another update when the wheels are built, and again after I've ridden them a couple of times.