Your link is to a regular "DP Dual LNBF" which is identical to the LNBF that is on the SuperDish 121 for the 110 satellite, and
yes it will work to pick up 129. More than likely the LNBF you are using for 61.5 is also the same.
You must be thinking about trying this.
If so, may I suggest that before you go and buy another LNBF, you give it some thought on how you are going to mount it to the SuperDish 121.
I furnished a picture where I duct taped it. I knew I would not be leaving it up permanently with tape, so I did not use as much tape as I could have, but even so, after awhile it will loosen up.
It looks like the pictures on the other link were lost, but I believe it may have had some clamps as well as one or more spacers to obtain maximum signal. It may also have had the shroud removed. I don't know if the shroud helps to keep it hot or cool, but without the shroud, there would be more options to possibly mount a bracket for the additional LNBF. With the Shroud, your options would be to duct tape it, or maybe using some small nuts and bolts to secure it to the shroud after drilling holes in it.
You may also want to consider using an I-bracket to help mount it.
http://www.dishstore.net/index.php?cPath=65
A satellite meter, or a TV next to you while looking for 129 will be required.
You may want to experiment by temp using the LNBF & I-Bracket from your 61.5; or even the 110 LNBF. This way, before you buy extra parts, you will see what issues you may have when trying to mount it at the correct angle and distance.
Good luck.