8:57 AM PT -- Trump is taking advantage of Hulk's viral moment ... 'cause the former president's campaign is now selling the same cutoff the wrestling legend rocked on stage!!

Folks can cop the merch with a donation of $35 or more ... and we take it it'll be a hot item with the MAGA crowd following the memorable performance.

The Republican National Convention stage looked more like a wrestling ring Thursday night -- at least for a few minutes -- as Hulk Hogan ripped off his shirt and fired up the crowd with an impassioned pro-Donald Trump speech.

The WWE-style moments all went down at the Fiserv Forum in Milwaukee ... about an hour or so before Trump formally accepted the GOP's nomination for President.

Hulk, who said he committed to speaking at the event following Saturday's attempt on Trump's life, repeatedly praised the former Prez ... all while speaking as if he were in the center of a squared circle at WrestleMania.

The 70-year-old called Trump his "hero," name-dropped legends like "Macho Man" Randy Savage -- and then dubbed DT and J.D. Vance the "greatest tag team of my life."

Hulk really got fired up, though, when addressing the assassination attempt. He slung off his suit jacket, tore through a black tank top to reveal a red "Trump/Vance" cut-sleeve T-shirt -- and screamed, "Let Trump-O-Mania rule again!"

"Let Trump-O-Mania make America great again!" he added.

Hulk -- who's been pals with Trump for years and even joked back in 2015 that he wanted to be his Vice President running mate -- then sat with Trump's closest family and friends throughout the rest of the night.

The wrestling legend, of course, was not the only celeb to hop on the mic at Trump's big night ... UFC honcho Dana White was the one who actually introduced Donald at the conclusion of the evening.

White spoke glowingly about his longtime buddy for around six minutes -- before handing off the stage to the man of the hour.