Mike Dineen used around 3,000 bricks to build the structure over four months and has now submitted the design to the toy company's website.
The 41-year-old is now hoping to get 10,000 votes so the Danish firm will consider using a scaled-down version of his structure.
"When I realised it didn't I thought 'why not?' It's such an iconic landmark. It deserves to be on the shelves."
The Forth Bridge was designed by Sir John Fowler and Sir Benjamin Baker and was completed in 1890.
The Unesco World Heritage Site is 2,467 metres in length, has survived two world wars and the striking red structure is still in use for railway services across the Firth.
Inspiration for his 1:352 scale scale model comes from Mr Dineen being able to look at the bridge while he works at a site in South Queensferry.
It took about one month to construct and three months of "trial and error" in the design process.
Mr Dineen said: "It's safe to say I was anxious that it might end up looking weird.
"I'm absolutely delighted with it."
Since then he has constructed models of Navid's shop and The Clansman from BBC TV series Still Game, including figurines of the characters.
Votes for his product idea can be made on the Lego Ideas website.
Mr Dineen had more than 300 supporters at the time of writing.