iirc, those films are Miramax/Dimension and are now owned by Paramount (films from 2005 onward are Weinstein/Dimension and have been owned by a different company, hence why I imagine the RZ ones are easy to find). The three separate discs that were released early 2010s are currently OOP but will be rereleased on 9/22 as a one disc triple feature, running about $15.

Based off everything I have read, H20 and 6 are almost entirely not worth it, individually or in a three pack. Poor might-as-well-be-DVD like transfers, no 5.1 audio - just stereo. No special features. Resurrection seems to be the best of the bunch.

The Producers Cut of 6 used to be readily available (I got it this time last year for about $7) but currently looks to be OOP as well, considering the current $80+ prices.

Edit: here’s the upcoming, reasonably priced triple feature disc:

https://www.amazon.com/Halloween-3-Movie-Collection-Blu-ray-Digital/dp/B08D55N23N/ref=mp_s_a_1_3?dchild=1&keywords=halloween+3-movie+collection+blu-ray&qid=1599923511&sprefix=halloween+3-movie&sr=8-3

Edit #2: and in case you wanted them individually, there are no plans for them to be released any time soon aside for the 3-pack.