On Amazon, I have no idea. But elsewhere the right strategy seems pretty straightforward. Search, search, and more search.Since that niche is highly specific and utilitarian (rather than brand- or image-driven), I'd recommend concentrating on (1) search, (2) search, and (3) search. Other marketing channels such as social media, radio, etc. won't give you anywhere near the bang for your buck.

These days, that means mostly SEM. Leveraging the right domain(s) can shave off some long-term expenses. SEO will be important too. Make sure you appear preferentially in the most relevant search verticals in the most authoritative fashion.

Basically, get the maximum of clicks with a minimum of cost; then be sure those clicks convert to sales through your site. Concentrate on gathering and evaluating data from SEM campaigns and on-site sales funnels. Try some A/B testing on your website and domains / URLs being displayed. Gradually your ad spend will become more efficient.