The design and wearing of the sheath are important considerations. Upper arm/lower arm/calf/thigh/belt/float/etc. How attached? How released? How re-sheathed/reattached?
I made a couple spikes a few years ago, using cheap, readily available thermoplastic chainsaw-file handles and awl spikes. The red thermoplastic file handles were very good: £1 each and they produced a result not unlike the lovely but extremely expensive Rob Allen ike jimi spike. I attached the handle by a loop of elastic bungee to the bottom of a metal-tube sheath (made from a piece of old, stainless steel, telescopic car aerial (BrE.)/antenna (AmE.)). I
looped it to my weight-belt with the elastic loop, which both secured spike & sheath and held them together. It worked quite well, when I drew the spike from the sheath, the metal sheath slid behind the belt and freed itself quite easily. Rethreading it back on the belt was a bit more fiddly but not too bad - an area for improvement though. Unfortunately, after spiking one fish I dropped it while trying to rethread it to my belt and by the time I had finished stringing the fish (a v. good mullet which I did not want to loose) was unable to locate it*
. Perhaps I was sloppy dropping it, as my spearo dagger & fish-stringer spikes all have lanyards**, so dropping them is not a big deal. However, I felt over-equipped, as I was already carrying a spearo-dagger/dive-knife, I had a good, long, sharp spike on my RA float-stringer and a rather poor but usable little spike on my (Beuchat/Omer?) nylon waist stringer. The little iki jime spike on your person probably is the fastest & best way to dispatch fish tho'.
* Despite the red handle (red light is absorbed fastest in seawater as depth increases, which makes it somewhat camouflage/grey as depth increases) and being relatively shallow water, close to shore - too much weed , sea movement - and excitement .
**Long ago, I dropped my cheap spearo dagger while out diving but managed to recover it the next day while re-tracing my dive route, it was on top of a reef glistening in sun - couldn't believe my luck! I had lost a cheap but very nice dive knife prior to that. So after than I added a 30 or 40lb monofilament lanyard to the dagger, stong enough to hold it but weak enough to cut/break in extremis. That was maybe 6-10 years ago and I am still using the same spearo dagger.
It's a pity that the Rob Allen ike jime spike isn't more like £10-£25 than £40-£50, that would solve the problem for most of us!
I expect the sheath is the expensive bit but all quite simple/basic.
