They still sell them new. e.g.:

https://www.amazon.com/dp/B00006IAAL

These ones?

https://www.amazon.com/Maxell-108562-PacksMaxell-Recording-Protective/dp/B00006IAAL/ref=asc_df_B00006IAAL/?tag=hyprod-20&linkCode=df0&hvadid=459527314024&hvpos=&hvnetw=g&hvrand=1098711241909371353&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9013711&hvtargid=pla-433881646245&psc=1

These have a screw together shell. Simply unscrew it, remove the excess tape and clip it back onto the reel. There's a little clip on the reel. It's not too complicated. Then close it up, done