Hi and welcome!
I am very sorry for your loss. You are welcome to post a tribute to the boy you have lost in our Rainbow Bridge section if you wish to.
The by far safest way of bonding bereaved guinea pigs of all ages and genders is by dating them under expert supervision at a good rescue; this means that the piggies decide who they want to get on with. You maximise to the chances of finding 'Mr Right' before you commit and minimise the risk of coming home with a piggy that is not accepted by Oreo.

By making the extra effort to adopt from a rescue with mandatory quarantine and medical care, you can be assured that any piggy is the right gender and healthy upon adoption and does not come with some unplanned issues in its luggage. You also have the rescue to support you during the settling in period and if there is a fall-out during the whole life time of one of their adoptees. That is a lot more service and security than you would get from a shop.
You can bond Oreo with a baby boar (please double check the gender upon arrival) if you wish to, but you have to be aware that not all baby boys are accepted as many people expect. If you do the bonding at home and bring home a piggy on spec then you have to always have a plan at the ready.
There is no difference in bonding babies than to any boar-boar bonding at any age, apart from the fact that the baby cannot challenge the hierarchy; that comes when the testicles start decending around 4 months of age. Only then it decides whether the boys are character compatible or not.
What does NOT work is boar trios; sub-adult boar trios have about a fall-out rate of 90% during the teenage months (4-14 months); they are the worst possible combination, only surpassed by boar quartets in instability.
Alternatively (and only if you have access to a good vet with experience in guinea pig neutering or small furries operations that you trust) you can of course think about neutering to allow Oreo to live with a sow after the obligatory 6 weeks post-op wait. Cross gender pairings are the most stable of all guinea pig pairings.
Please take the time to read these guides here; you will hopefully find them helpful for you to make an informed decision. You can find links to recommended rescues we can guarantee that you are in safe and knwoledgeable hands in several countries in the bereavement guide and lists for recommended vets in the neutering guide.
Looking After A Bereaved Guinea Pig
Adding More Guinea Pigs Or Merging Pairs – What Works And What Not?
Boars: A guide to successful companionship.
Bonding: Illustrated Dominance Behaviours And Dynamics
(Our extensive bonding guide includes all stages from the preparation, typical behaviours and dynamics, special aspects of various gender combinations, and also includes the dominance phase, which lasts around 2 weeks after the introduction)
Neutered / De-sexed Boars And Neutering Operations: Myths And Facts
Since we have got members and enquiries from all over the world, we find it very helpful if you please added your country, state/province or UK county so we can tailor any advice always straight away to what is available and relevant where you are and help you with recommendations as much as possible. Your options depend largely on your local rescue and vet access. Please click on your username on the top bar, then go to account details and scroll down to location. This makes it appear with every post you make and speeds up things. Thank you!