The former NBA star went on a NSFW Willy Wonka-level tour of RealDoll's Las Vegas facility Tuesday ... full of totally nude female sex dolls hanging on hooks and huge realistic male organs -- and, Lamar got to touch everything in the facility.

Ya gotta watch the clip ... Lamar's walking through the facility -- picking up dildos and whipping them around before copping a feel of one doll's boobs, touching her all over and saying it almost makes him want to design women's fashion.

We're not sure he's got a Vogue shoot in mind ... but, you never know!

Lamar's manager, Gina Rodriguez, tells TMZ ... Lamar first saw RealDoll in a news story about a month ago -- and knew instantly he needed to get one for himself.

We're told Lamar was in Las Vegas this week for his birthday ... and, he decided it'd be the perfect time to go find himself a silicone GF -- and, sounds like he did 'cause the money changed hands and the doll is under construction.

The dolls usually go for between $8K and $20K, but we're told RealDoll cut Lamar a deal -- though we don't know what kinda discount he got.

RealDoll doesn't just do prepackaged dolls BTW ... Lamar opted for a custom order -- picking and choosing his new bang buddy's lady bits.

We're told he wanted the doll to have voluptuous curves ... and based the face on his ex-wife Khloe Kardashian's. Gina tells us Lamar thinks this Khloe-like sex doll will be perfect -- because he can do whatever he wants with her sexually. No word on how Khloe's feeling about this new tribute.

Khloe and Lamar were married from 2009 to 2016 ... but Lamar's drug and alcohol abuse and infidelity ultimately tore their marriage apart. They don't have any kids.

Like we said, the doll isn't finished yet ... but, we're told Lamar should get it before the holidays -- perfect for a kiss (or more) at midnight on New Year's Eve!