As there are / if there are some girls and guys here who actually want to be locked and always find it hard to stay away from the keys..like me... and don't have somebody to lock them I wanted to share with you the solutions I know.

So there are commercial keyholding services, such as Locked in Keyholding, a brand of Locked in Lust, a cage manufacturer, that you can use - being locked up for a year does cost about 100€, two years do cost about 150€.
Then there are community led keyholding services like Emlalock. Therefore you need a key safe you can set to a variable code. You get shown a code you have to set and get shown some fake ones right after you locked your keys to make sure you forget the right code.
You have tobe honest about it as it is eays to cheat using this method. The site provides your keyholder / you with a link people with an account can increase or reduce the set time with or just define the time you will be locked. By the way - you can choose whether you are given the chance to be unlocked for cleanings regularly. This site is said to work with a sort of photo-approval. (Don't kill me if I wrote something wrong here, was a pretty long time ago since I did use it last time. Just check it out if you are interested in using it.
There also is the app Chastikey which works nearly identically, just without photo approval.
There are also sometimes nice people in forums that provide a private and free keyholding service like you can find it on Chastity Mansion
Or store them in a place that's not easy to access. Like for example freeze them in an ice cube. If you get week it will take some time till you can get them and you are hopefully not horny anymore.

I know, it's all not an ideal solution, but it works when you're willing to let it work.