Middle-distance runner Blake, 25, won silver and bronze at London 2012 as well as the T36 800m title at October's IPC World Championships in Doha.
Blake, who has cerebral palsy, is struggling for sponsors to supplement his funding for the Rio Paralympics.
"Without funding, I'd struggle to continue," he told BBC Radio Solent.
Blake, from Dorchester, was speaking as a campaign was launched to encourage the public to generate funds for the team.
Supercharge Paralympics GB hopes to ensure Britain has the "best prepared team" for Rio in September.
"The bigger sponsors and the bigger companies focus on specific athletes and it's pretty hard for cerebral palsy athletes to get any significant sponsor," Blake said.
"They focus on the athletes with a visual disability that you can physically see."
Blake, who also won T36 400m silver in Doha, receives funding from both UK Sport and Camelot based on his performances at major championships.
But he admits meeting expenses for travel, accommodation and new kit is difficult.
"I can only do so much in keeping on handing out begging letters, but I've got to focus on training as well," he added.
"Crowdfunding is one way of going about it, but I don't really have time for that. I'm just doing what I'm doing really and hoping something comes up."
Former GB wheelchair basketball player and now broadcaster Ade Adepitan has sympathy for Blake.
"I think the next level in the progression of the Paralympic movement is where our athletes get sponsorship from the large brands, in the same way able-bodied athletes do," he said.
Paralympics GB men's team captain Paul Blake believes sponsors are more interested in supporting "athletes with a disability you can see".