I'm pretty sure the bulk bin spools (black, white, ecru, grey) from Joann's still have the notch. Yep, seal it with acrylic nail polish or cut it off.
I am a user of inexpensive threads and have gone to the Gutermann Mara 100 from Wawak. It is really inexpensive and is the same as the Gutermann Sew-all. Gutermann is now manufactured by American and Efird, a company that actually still has a US manufacturing plant!. Anyway it comes on a beautifully formed, cross-wound spool, which is easy to put on the spool-holder, but I use a thread holder out of habit.
As an aside, I have 30 year old quilts that I have sewn with polyester thread, machine washed and dried numerous times that have held up extremely well. The only issues with them are that the few batiks I used in them. The batik fabric is actually disintegrating where the wax clearly was (and yep these were Hoffman batiks).