How to get a chihuahua to stop constantly jumping..?

I have two male chihuahuas that have a run and a doggy door leading them into part of the office. They are in there because they are not fixed and plan to breed them one day. I also have a female and so that is why they are kept apart. Now one is a mellow fellow, and thus is fine. The other is a jumping bean.. literally. He jumps against the gate over, and over and over again until i get so tired of it i yell at him.. we have tried teaching him to stop, but since he was a puppy he has jumped against doors, counters, gates.. anything in his way... i looked up the anti jump harness, but that won't work for him.. he's not 20 pounds.. lol so.. what should i do? is there anything smaller that will work for him? I'm not getting rid of him, not fixing him, and am not letting him out with my female, he is perfectly fine where he is. He just does it to piss me off i think....