The wholesalers are there, but most will not consider selling just a couple of units, and then if they do they it won't be a wholesale price. Wholesale pricing is based on volume sales, the more units you purchase, the cheaper the per unit price.
Unfortunately the wholesale market isn't an option for you at this stage with your current purchasing restrictions.
With mobile phones, even if you could afford to buy in high volume, you would have to sell at low margin to have a chance at making any money on a site like ebay, the market is just too saturated and super competitive.
I think the bike helmets are a good solid idea, that is if you are talking about laying some custom colour down being that you have the painting background. You don't need a wholesale source, you could buy cheap ones from ebay itself, lay some magic on them and flip them over back on ebay.
Custom painted helmets would give you a distinctive market to aim at, and from there you could extend the genre to include bike tins and other related products to suit your core market.
If you have the ability to lay some nice clean paint on a helmet, that has far more potential to make you money than trying to compete with the other 10 million sellers around the world all trying to sell mobile phones.
You don't have to do murals or graphics, there's plenty of straight out custom materials that anyone with a good gun and some good training in the industry can make work.
In the USA you should check out asla corp or House of Kolor for some ideas, but PPG and most others suppliers have a good range of trick finishes these days.
Combine your passion and your skills, and you might just create yourself a market, and it would be a market with limited competition............the best kind : )