Sure ID,
I make the sides out of thick, high impact plastic cut from those thick plastic buckets that pool chemicals come in, or any similar source (lids and bottoms of the buckets are the only places to get flat pieces on the buckets, but I've also used those plastic license plates and sacrificed other box-type plastic containers). For the axle I just use a brass bolt. I've used a short piece of PVC as a spacer, or just stacked four or five nuts on the bolt as spacers. I use a lock washer under the outer nut. I drill holes around the periphery of the sides so I can clip in a snap bolt. My little homemade reels look similar to commercial offerings, but I actually prefer my own as I can size 'em just so to fit my hand and get the maximum size (and therefore the most and/or thickest line) that I can easily handle.
I'm amazed at how few divers carry reels as a regular piece of equipment.. I probably use a reel on 20-30% of the dives where I was "just carrying it." It sure makes those little impromptu searches easier, or marking the anchor when it's a little further from the site than anticipated, or leaving a line to mark a desired exit point on a beach dive, or connecting two pieces of a site that can't be seen from one another... and on and on and on...
Rick