@annieeg In the mid 80's I bought a new sewing machine direct from Brother in Audenshaw, my sister worked there so I got a huge discount it was Brother Compal Opus 845 and a side cutter attachment was included with the accessories. It was the only sewing machine I owned for nearly 30 years and my goodness, did it get lots of use!
I still have it but have never used the side cutter, so here it languishes. I bought an overlocker at the same time but omg that was completely new to me and I sold it years later never having done other than look at it with bewilderment.
Might be tempted to get the old machine out and try the side cutter, see if it works, I know the machine still works fine, Mike had it out and put it through it's paces a couple of months ago. Not bad for a 30year plus 'computerised' sewing machine.
Here's a youtube video of the same model, has a different badge, Compal L but is an identical model.
https://www.youtube.com/watch?v=fb9vdIj0a1M