I bought a Bora-WTX track saw track and a generic fits-all sled. It didn't fit my Ryobi circular saw. So I built this piece to go between the saw and the track. Ball bearing slides would be better, but two of these at either ends of the saw work fine.

I made a hole for a small 1/16" x 1/4" magnet, but it's not strong enough, so I added zip ties and drilled two holes in each corner of the sled.