Hi!
The best way would be to take Bramble rescue dating so he can decide whether and who with he wants to get on; it means that you come home with a new companion only if there has been bonding success. With the rescues I have linked to, you are also guaranteed to only adopt a healthy, fully quarantined and properly sexed guinea pig.
There are a number of UK, US and Australian rescues that offer this service. Sadly as you have not added your country, state/UK county to location in your account details (via clicking on your username on the top bar) to make it visible, I cannot give you any more detailed advice.
Vetted and recommended good standard UK rescues:
Recommended Guinea Pig Rescues
Vetted and recommended good standard rescues in some other countries:
Guinea Lynx :: Rescue Organizations
(Please note that not all listed rescues do offer boar dating, but a fair number does).
If that is not an option for you, you may need plan for a long term alternative, like companionship through the bars as next door neighbours with full body view/scent and voice interaction for optimal communication and stimulation.
These guides here all deal with your question. You may find them helpful:
Single Guinea Pigs - Challenges and Responsibilities (chapter 2 deals with various companionship options with their pros and cons)
A Comprehensive Guide to Guinea Pig Boars (chapter IV is about companionship for single boars)
Bonding and Interaction: Illustrated social behaviours and bonding dynamics (our detailed bonding guide)
I hope that this and the links which are looking at the issue in more detail will help you.