Hello Janice,

I am not sure I can help directly, but I am sure there is a way to do it. Though, you need to contact a company that makes sliding doors, since lanai and screen companies rarely do this - it is rather different technology.

We create sliding enclosures - the whole thing is divided into segments and they slide telescopically into one another - but in my opinion, your stading aluminium frame can be used to house the new door like here in this Houzz image:

Patio Enclosure · More Info

It would be custom made size that corresponds with the size of your lanai opening (alu frame) and than is fitted in. Depending on the material and sturdiness of your enclosure/lanai/screen construction.

Plese see more examples of sliding doors here on our US website for your imagination. You can contact the manager to see if he can help you, since this is such a specific request. Again, depends on the construction itself.

Have a positive day and best of luck :-)

Jiri