Just wanted to share my experience of buying the bricks in the parks in case it helps anyone out who's looking to do the same!
I was in WDW last week and decided to just buy the bricks while I was there since I wasn't 100% sure what was written on our bricks (we have two, but I was a literal infant when they were purchased and it's been a few years since I actually looked at them). I went to City Hall first to get the voucher and the actual location of the bricks. I was expecting to just get one $10 voucher, but when they saw I had two in the system, they actually gave me two vouchers, which was really nice! They then gave me the location of the bricks so I could go see them. Interestingly enough, my grandparents' original brick was apparently broken/removed at some point, and reinstalled in 2008 next to my family's original brick from 1994 (while their original 1994 brick was in a different area). So my friend and I spent almost 10 minutes searching for a brick that no longer existed! It was when we decided to look for my family's brick that we found the "replacement" brick. So we found it interesting that the database only had the original brick's location and not the replacement's. Kind of a bummer the original was no longer there, but it was really nice of Disney to replace it that many years later.
I ordered the replicas at the Co-Op in Disney Springs (you can also get them done in Tomorrowland). It was super easy to use the kiosks there to personalize the bricks. Only issue I came across was the replicas had to have a full date on it (our originals only had the year listed) but I decided to use the bricks' numbers for the month and date so that actually worked out nicely and is now like a little hidden message! The kiosks then printed out two separate receipts that I brought to the cashier along with the vouchers. They were ready to be picked up 30 minutes later and came out perfect!
They do have a bit of weight to them and come in a decently sized cardboard box for protection, so just mind that when considering luggage space/weight. I didn't want to take them out of the boxes because I was more worried about them breaking in my luggage than the weight of them, but everything was fine and they both came home in one piece!
My grandparents both passed away last year but they always loved Disney, so it was really important for me to see the real brick one last time and to get the replica. It's really a great and unique souvenir, even if you didn't have a brick originally!