1-1/2" and 1-1/4" adapters of all flavors are commonly found in any big box store, which are all set up to provide for Ikea plumbing.
Thanks for joining and posting the forums.
With many new members looking for advice and answers, be reminded that good photos and illustrations always invite an audience that can give faster replies that are less generalized and more suited to your exact needs.
Try to provide at least two photos. Include a closeup of the attention area so we can identify fine details, and include one zoomed out so we can see the rest of the room and things nearby, adjacent areas, floors underneath. Use a black marker to write on blue painter's tape or bright colored Post-It's to mark areas of interest, there is no need to modify your photos with fancy text overlays. Use a low resolution setting, as the website can reject images too large. Take as many photos as you can, choose the best ones that are clear.
Do include diagrams for plumbing and supply line projects. A scan or photo of a hand drawn illustration done quick on paper is usually easier for most to create than trying to make one in a computer app. We don't need architect plans, just something simple to help us understand your idea.
Make sure your location is in your member profile, this tells us where you are so other members here with experience in your area may give you specific recommendations that may apply to your seasonal weather conditions and state code.
Edit the subject title of this post to summarize the exact nature of your issue. "Second story toilet is clogged" will attract more readers than "Help I am in desperate trouble!" which more will ignore, possibly leaving your post unanswered.
While waiting for replies, please make some effort and take the opportunity to search these forums extensively, it is likely that many in the past had your similar issue, and you may find solved solutions quicker than the many days it can sometimes take for you to get answers you want.
As you solve your problem to finish, kindly please follow up on this thread you created and update your progress, so future members with your same problem can see that this may also be used to help and inspire.