you should be able to search out several bike sites online that have reviews on lids; one that comes to mind is "web bike world."
clearly a helmet is something you don't want to scrimp on; if you can't afford a decent one, you can't afford to have a bike. on the other hand you don't have to break the bank to get a good one.
number one is look for the snell rating; number two is fit; other important things are weight (both for comfort and inertia when you are banging along the pavement) and ventilation. fit is something you just have to try and may end up being the one thing that determines the brand you buy as different brands have different ideas on what shape a rider's noggin should be.
i use a scorpion; snell rated, best fit i've ever had, fairly light, stellar ventilation, and you can get them for about $160.
whatever you do, you should trash the old helmet; it could break in half on impact; the liner may have lost its resilience, etc. and forget about used or ordering online; check them out in person and find one that fits snug and comfy and with all the above virtues.
enjoy, and i hope whatever you spend on a helmet turns out to be wasted money
