Kathy,
Insurance is based on risk assessment and the greater the risk, the more difficult it is to find a product that's going to suit your needs or if you do find one, then it can come at a premium. Short term car insurance in itself poses a huge risk to insurers because if during that short time that you are being insured you make a claim, it can cost considerably more to settle the claim than what you're paid for getting the insurance cover. Statistics have probably shown that people over 21 are less likely to be involved in an accident and make a claim, hence insurers have put an age restriction for temporary car insurance. Having said this, there are just a few insurers who will take 21 year olds on board as most are looking for people who are 23 or over 25.
If you're looking for a month's insurance, then you should consider going on eCar Pay As You Go car insurance as this enables you to get cover one month at a time. So you can get 1 month's insurance initially and if you want more cover, then buy an additional month. The good thing about this insurance policy is that there is no age restriction (as long as you have your valid licence). Have a look at their website and see if that's something that would interest you.
