Plucky podger lives to prod another day

Just before going to bed last night I had one of those 'it won't work but there's no harm in trying' ideas... and it did work!  I have retrofitted the broken rag rug tool with an external flexible tensioning device - i.e. I have wrapped a rubber band around it, and amazingly, it works; it provides enough force to hold the fabric strip and pull it through the hessian, and leaves a long enough point to poke through. Hooray for Heath Robinson!