If we're going to delve into non-JAV tentacle vid, there's more out there than you might think.
First, you're lucky you found "The Visitors." PTnA apparently just got smacked with a bunch of cease-and-desists, and dropped all their Wicked uploads (along with those from lots of other companies). That's just PTnA, but who knows how far it goes.
There's an "extras" disc and assorted stills floating around that suggest Michael Raven was at least considering having other actresses go a round with the aliens, and it's really too bad he didn't go that course.
The "Fucking Machines" series by Kink.com (also now on PTnA's no-go list) went sci-fi, sort of, with the 2010-08-16 entry starring Tori Luxe. She's "alien abducted" in her sleep and wakes up bound to a table under a device that proceeds to probe her 'til she likes it. It's very good, but the entire budget went into the machine--the aliens apparently fly around in an ordinary examination room and employ hardware-store cord to restrain their human subjects.
JM Productions' "Perverted Stories" series were even lower-budget with varying results. The series' vignettes would often be just plain ol' gross, or amazingly silly (you haven't really lived until you've seen a woman double-penetrated by guys made up as pterodactyls), but they had the standard Bigfoot entry, a green Martian encounter, and a giant dildoctopus in "It Came from the Deep." Most of the time you couldn't even see the stagehands working the tentacles or the paint coming off...
ZFX was even lower budget and the relevant videos are sadly hard to find, but many of its movies featured alien worms, dirty ghosts, tentacle impregnation, r**ist potted plants and spiders, and so on, although things always turned to hard SM and REALLY cheap effects.
The dearly-missed-years-later website "Galaxy of Terror" (named for, but not directly related to, the movie) was a great resource to learn about these movies, AND the mainstream Hollywood and European films with at least a LITTLE monster-on-woman hotness--from Jessica Lange's nipple-slip in "King Kong" to the alien-vacuum r*** in "Oversexed Rugsuckers from Mars" to "Inseminoid" to "Xtro" to "The Beast Within" to "La Bete" to "Breeders" to "Crystal Force" to "Porno Holocaust." Ah, we'd sit through such total crap to catch just a few seconds of suggested tentacle action!
Maybe we need another thread...?
But one of these days, the California porn industry will get it right: "Progeny"-grade effects that are the real (male) stars of the movie, banging "Visitors"-level actresses. I MUST NOT DIE BEFORE THEN.