NormaCorcs are excellent. They are not rubber. They come in different lengths and grades depending on intended use. I bottled 300 bottles of wine with them last fall and not one single issue. You can buy them on Amazon:
https://www.amazon.com/Reserva-Wine...KX0DER&qid=1592224828&s=merchant-items&sr=1-2
The Reserva corcs are their best, and likely not needed by most home wine makers. I like the Select Green 300s. Good for 10-15 years, and likely longer. They are not green, but green in the environmental sense. I believe they are made from sugar cane.
https://www.amazon.com/Select-Green...KX0DER&qid=1592224828&s=merchant-items&sr=1-1
The Select 900 Normacorcs are their least expensive corc (sic), and that's what most local brew shops sell. They also compress easier for hand bottling equipment, though the Ferrari floor corker has no problems with the higher grade ones. Several vendors sell bags of just 30 on Amazon if you want to try them out.