Hi Bill, great idea! For online advertising, you have two main options that cover approx 90% of online advertising.
1 = Google and think primarily google Adwords. This means paying to come up on google searches and is great for fulfilling demand if people are already searching for a product like yours.
2 = The second “major” online provider is Facebook. Social media advertising is great to create demand with people who perhaps do not know yet that they need your product, but are likely to buy it if shown it.
I believe you might fit better into the second category? LinkedIn might also be an option because you can target based on industry and job title however for a $25 sale I think the cost of LinkedIn ads will be prohibitive and Facebook ads sounds like the place to consider most closely.
My suggestion would be to get a designer to mock up some ads for Facebook – it sounds like you have this capability inhouse? Then find a freelancer who can run some ads for you at a reasonable price for a one-off campaign. Don’t go for the cheapest person out there as you get what you pay for. But also this sounds like a one-off campaign for a short term product so you also do not need to speak to agencies who will mostly want to work on retainer models.
Ultimately, you want to test the waters with Facebook ads but please spend most of your money on the ads themselves, not designers or agencies to run the ads. If this sounds hard, it’s only because you have not been down that route before and actually it is very doable.
I am happy to help more if I can so ask away any further questions.