I have found parts on ebay, model 27 is luckily still reasonably common. There are
new replacement bobbins to be found, but the quality on them has varied. Vintage bobbins tend to be trouble free, (they might need a good cleaning though). I have a few times bought new 66 class bobbins and not all of them will go on the winder. I'm not that used to long bobbin machines. I don't mean to discourage you from bying brand new ones, just be aware of issues and as long as you have a few original you will easily spot any problems. I buy both new and vintage accessories from my machine.
You might get surprised by you old 27. I know two people who have taken a 28 (the 3/4 size version of your 27) as their favorite. On of them swear it gave the neatest top stitching on jeans and various fabrics, she had several machines to choose between. The manual for it is on the web, and it probably needs a bit of cleaning and oiling to run nicely again.
On ebay you will find old original parts, and Helen Howes in the UK is an expert at finding the hard to find parts. Model 27 went through some slight changes, so be carefull that parts for the winder and hand wheel is correct. You might like the treadle action, some look particularly for this feature. Early model 27 can be difficult to convert to motor and light, but the later ones that have a screw hole in the body under the hand wheel take a bracket, the same for both hand crank and motor.