Advice on business plans and finding an investor for a new product

Hi all

Bit of an unusual one and apologies to the moderators if this isn't the correct forum.

I have an idea for a new product which isn't on the market in the form I would like to create it in, but I know next to nothing about new products. I believe from reading up on it I need to create a business plan, product design and possibly a prototype to be able to attract investors.

I would be more than happy to sell the idea at this stage to a company/manufacturer but I have no idea if they would be interested without the above.

Can anyone recommend someone to produce the business plan in the first place (or invest!) and of course, keeping it money saving, what one would be looking to pay for this?

Thank you