The Tres Tria product looks nice, but pretty expensive for what is, essentially, a glorified pillow. Also, you may not want something that takes up so much room in your bed as your baby gets bigger.
I haven't used such an anti-roll-off pillow, but I have years of experience using a Co-Sleeper and recommend it highly.
I have three sons and have used the Arms' Reach Co-Sleeper with all of them. With my first baby, I borrowed my sister-in-law's Co-Sleeper since it seemed like another expensive novelty baby-care item and I wasn't sure how long it would be useful. We then purchased the nicest crib we could afford and had custom bedding made because that's where we thought our baby would sleep after the initial newborn period was over. It seems so funny now. . . .
We used the Co-Sleeper until my first son was over a year old, and we joked about how the beautiful crib in the other room was part of the "Baby Museum," since it was virtually untouched. We finally gave it away because it was all just taking up space.
When I became pregnant with our second baby, my sister-in-law was using her Co-Sleeper for her own baby, so we bought one of our own, knowing how useful it is. It is an essential, sanity-saving piece of baby gear, in my mind. I would say a Co-Sleeper and a sling or mei tai-type carrier are my top two pieces of baby gear--everything else is incidental. . . except maybe a couple good nursing bras and Lanisnoh nursing pads. That's it for my must-have list. ;) Breastfeeding is so much easier and more convenient when Baby is right nearby, and it's lovely to be able to nurse the baby to sleep and then scoot him over to the Co-Sleeper once he's asleep. I also feel secure in having my baby on either side of me at night while nursing, because even if he rolled a bit, he'd only roll into my husband one direction, and into the Co-Sleeper the other direction. It's a brilliant bed-extender. I value my sleep, and the Co-Sleeper has really simplified nighttime parenting and kept everyone happy and comfortable.
I know the manufacturer says the Co-Sleeper is intended for babies who cannot climb out of it, but its weight capacity is 40 pounds. A Co-Sleeper is shallow, compared to a crib, so it would be easy for an active baby to fall out. But my babies are never in the Co-Sleeper when I'm not right next to them, so we do not feel reckless about adapting its use beyond the manufacturer's suggestion. It has been a great investment for our family.
Our Co-Sleeper is the original full-sized model; I know they make a "mini" model if your room is small, but if it's an option, I highly recommend the Original size. I can keep a book, a bottle of water for myself, a folded extra baby blanket or burp cloth, and my glasses case at the foot of the Co-Sleeper as a little nightstand while Baby is still little and it's so convenient. We have the model that has a long liner/skirt and it looks nice in our bedroom, more like pretty furniture than baby gear.
I know families who use a Pack 'n Play type play yard as a co-sleeper bassinet and it works fine. I also know families who drop the side of their crib and make it a "side car" against their bed. There are lots of options, but as a breastfeeding mother, I think you'll always be glad to have your baby right nearby. My older two sons sleep happily in their own beds in their own room with no issues beyond a normal adjustment period and neither my husband nor I regret the time they spent sleeping near us.
Congrats on your growing family and best wishes!