OK, hitting on women at the gym can be a major no-no, but it can work out sometimes if you read the signals and make your move in a friendly, non-creepy way. For example, when she’s in the middle of a 30-minute run on the treadmill and sweating profusely, don’t approach her. If she’s got her headphones in, don’t approach her. If she’s deadlifting, obviously, don’t approach her.
One of the best- but probably a idea you never considered in your quest of where to meet older women is volunteering. Try your local homeless shelter or a senior citizens home. Now don't laugh, and don't think that the older women you may meet are going to be feeble and confined to a wheelchair! I'm talking the mature women who come to visit these people!
Be open-minded to all those interested in you. If you put an age-range or any other restrictive ranges into your wishlist, you could miss out on women who might be slightly outside those expectations but are ideal for you. It also sounds really bossy and perfectionist to list restrictive preferences and will scare off many women even if they fall within your restrictions.