I'm very sorry to hear of your budgie's escape.
And while the situation is heartbreaking, now is not the time to resign to it, there is still the chance of getting your budgie back.
You can look for him around your neighbourhood, place flyers advertising your lost budgie on nearby pet stores and vets. Since he is an older budgie, most likely his stamina is lower and there are good chances of you finding him on your street or other nearby area.
You can also spread the word on social media platforms, like Facebook, Twitter, etc.
If you happen to not find your budgie, you can spend extra time with your remaining budgie and closely watch his behaviour. If he is receptive to you, then you can strengthen the bond and if your budgie shows signs of adjusting well to this new reality, then you won't have to get him a friend.
If you do choose to get him a friend, it would be best to get him older male companion (4+ years old) as he may not be receptive to the high energy and enthusiasm of a young budgie.
I truly hope your budgie is safe and will soon be reunited with you.