Adrian..Those teeth look reasonable as a try. For new parts, C&D Autos had NOS Clutch Chainwheels, (a while ago) but there are still reasonable numbers of used chainwheels available on eBay.
Try tightening the big nut against the clutch centre, which should slide easily down the mainshaft splines to abut the thrust washer.
The nut and tab washer will tighten to clamp the clutch centre hard against the thrust washer. A new nut and a clean up of the gearbox mainshaft thread may be required, lots of nuts get butchered, the tab washer is essential. Correctly assembled the nut does its clamping before bottoming on the mainshaft thread. Various thickness thrust washers were originally available to align the chain and space the clutch sprocket from the chaincase. You could also loosen the gearbox/engine bolts (plus engine mountings) and try to move the box further to the drive side, moving the clutch position further away from the inner chaincase. Any circular shims to finely align the chain go between the splined crank drive sleeve and the main bearing inner race.
In an ideal world you replace with new both sprockets and chain, or be like me and select the best of the rest for a reasonable low annual mileage runner.
To confirm duTch, the rollers are 1/4" x 1/4"
Swarfy.