So, there are a few things that make me think you're not a startup...which means VCs are not your ideal source of capital. VCs don't generally do "retail", and they don't generally do "niche", unless "retail" is something entirely novel (like Amazon.com was in 1994 or whenever it started), and "niche" is something with huge growth potential (like Cisco when they started, the market had nearly zero demand for "ethernet routers" at the time, but within a few years demand was astronomical and Cisco profited from their prescience). That doesn't mean you shouldn't get additional funding...it just seems likely you shouldn't waste your time on VCs or tech angels, which is what most folks around these parts talk about.
Other kinds of funding might be appropriate for your growth plans, though, like bank loans, lines of credit from your suppliers, etc. One reason startups don't fund through loans is that startups are too risky. A four year old retail business that has consistent sales over a long period is not risky. It's generally quite predictable from a risk perspective, and banks will trust you to use their money wisely.
There's also traditional friends and family investment, or you could bring on a new partner who brings money, expertise, and business relationships. The latter is probably what I would be thinking about, if I were in your shoes. It sounds like you need someone to help you grow beyond your current vision and into something larger.
Or, if you're making enough money right now to live on, and hire someone to take away the day to day processes of running the business, you have some other options that don't involve loans or giving away equity. You could try thinking like Amazon. I don't mean "imitate Amazon"...I mean, start thinking of new ways to leverage your existing technology and infrastructure and customer base. Did you build your own shopping cart software and inventory management tools? If so, can those be used for some other purpose? Could you open sister sites selling other products? Could you partner with local companies that want to sell their products online? Could you build out an affiliate system? Could you use it to sell virtual goods, like ad inventory? Can you make your customer base worth more? Amazon sells ads on their site, lets other retailers sell through their site, and has dozens of ways to make every customer worth more. Again, don't imitate Amazon (because you can't beat Amazon at their own game)...just start thinking like they do...always evolving, always figuring out new ways to provide additional value for your customers.