I am trying to disassemble by bedframe and the Screwdriver that I have seems too loose. Where can I find a screwdriver to do this?
It is called a "hex key", "Allen key", or "Allen wrench".
You can also find socket wrench tools with this hexagonal drive shape. Hex key socket wrenches are almost always stronger than Allen keys, and less likely to round out the screw head.
Both the fasteners and the tools shipped with Ikea furniture kits are necessarily the cheapest that can still do the job, so it should be no surprise that the wrench seems too loose. You may need to use a slightly larger hex key tool, even if it is nominally the "wrong" size.
If the next size larger hex key is too large, try one from a different standard, i.e. the next size metric for a SAE screw.
Once you have removed the cheap Ikea screws you should replace them with better quality. "Star drive" would be the best; purchase the screws and driver together.
As a last resort before drilling it out if it becomes to stripped to remove. Find a slightly larger straight slot screwdriver and expand the current Allen driver contact points. Then use a 6 point star driver or being furniture just tap the screwdriver into the fastener and remove and replace it since it's not likely to be corroded.
You need 4 mm, 5 mm or 6 mm Hex key (a.k.a Allen wrench, Inbus) for IKEA furniture. I recommend to buy a screwdriver bit set or a hex key set, because these are the most common hexagonal socket sizes. (I have 2 hex key sets and 4 different screwdriver bit sets, and all of them includes these sizes.)