John has it right . . . there won't be much, if any, respect for new procedures so it is important to determine what pieces of ISO 20000 SMS you already have in place. Take the standard, go through it and start checking things off the list and/or reference what's already covered. I'm going through an ISO 20000 SMS implementation project now and, considering cultural differences and people being people, this is the best avenue to take IMO. The QMS will integrate the SMS, with a basic SharePoint (file structure-like) management system set up with categories that will show documents fulfilling 13485, MDSAP, 20000, etc.
There are various requirements checklists and such that turn up through Google search, but it's not that difficult to read the standard and map out what they tell you that you need to cover in an Excel sheet. From there you would need a reference to what document, record, or other process is covering that in your system, probably including a group ownership reference, and you will have created a system map document. If there is anything else it would be useful to map to, for example if you have an overlapping ISO 9001 or 27001 system, including that content in the mapping reference might be helpful, to help keep it all straight.
Whatever template you turn up won't be fundamentally different or better than just making one. I did make one awhile back, and for lack of places to share it from I've just uploaded it to a Facebook tea group I'm the admin for (so I guess that tea related service companies could use it to certify to ISO 20000?). I made it a long time ago and this version may not be updated for the 2018 version change (it's probably not, if clauses shifted around a little, or a lot), so checking it line by line would make sense instead of just going with it. At a minimum it's one clear example of what I'm talking about, a simple mapping reference.