Hey Shane, you would need to use a micrometer to find the diameter of the hub and I see there is a taper at the ends of the hub that could cause chain Alignment problems. So for an example if the hub is 1" 1/4" and the adapter is a 1" 1/2" you need some 1/8" spacers from eBay or cut some From tubing cut into thirds to shim in between.
This one is for a 1" diameter hub but it comes with shims so you can use if for smaller hubs but I just don't know if it would fit the one you have. I got one of these sprocket adapters for a hub with peddle side gears and I didn't need to use the shims, it fit perfectly. Also, it's kinda expensive but it is a solid well made part. Sorry, that's all I got. I just don't know if it would fit on that small hub. What size it is?
Another way to measure for the hub adapter is find an open ended wrench. Start with a 7/8" wench and slide over the middle part. You could use a metric wrench also and then convert to the nearest standard measurement. If the wrench fits without any play, then you need that size or a bit larger with the proper shims. After that, you should measure the inside width of the hub and compare with the dimension of the chosen adapter to see if you have enough room for chain Alignment.