The shuttle and bobbin that came with my Singer 28K
Original bobbin (top) and shorter modern replacement (below)
Note that the thread guide travels past the end of reproduction bobbins
More Internet based research threw up a couple of workarounds. The first is to bypass the thread guide and use your finger and thumb the second is to build up one end of the bobbin with blue tack. I am not keen on either but by using the former I managed to get one of the new (short) bobbins loaded with thread. If you can get this far then you will find that the thing fits inside the shuttle and the machine will sew happily without further incident.
A little while later I saw some more new bobbins advertised as being longer than most available and to fit Singer 27/127 and 28/128. I thought I would try them. This next batch are longer than the first ones I bought but they are still a shade shorter than the original part. They sit better and do not seem prone to slippage. Again if you can get them filled (I simply stop when the thread guide gets to the left hand end of the bobbin, lift the thread out, wind the bobbin past the high spot on the heart shaped cam, put the thread back in guide and continue repeating the step as many times as required) they fit inside the shuttle and the machine will sew well.
During the last couple of weeks I have been lucky enough get hold of some old [original?] long bobbins. I have two basic patterns. The first looks a lot like the one that came with my machine some have a hole in one end and others dont. The second are domed, rather than pointed, at one end. Being second hand bobbins each one came prewound with several colours of old cotton and silk thread. The thread had attracted moisture which has caused light surface rust on the spool of the bobbins but this can be smoothed off with metal polish and the brass ends shine up a treat! Best of all, as they are original parts, they have a great original fit in the bobbin winder. This really does speed things up.
My advice - Go to the effort of sourcing some original old style bobbins they will make using a VS sewing machine a much more pleasant experience. From what I can gather most Singer Vibrating Shuttle machines were supplied with a bobbin and four spares when new. Millions of VS machines were manufactured so there must be tens of millions of old long bobbins kicking around the world even to this day! I bet most of them are in the drawers of treadle bases or old tobacco and shortbread tins.
My question - Who is making these other bobbins and why, if one is going to go to the trouble of manufacturing obsolete parts, don't they make them to the right spec?