"We did use a plastic bag in the existing toilet, Susan. I really can't figure out how you'd fit a bucket in ours though. I've noted on trips to the US that American toilets seem to be somewhat larger than NZ toilets..."

Well, I can't see any reason to put a bucket into a toilet...

1) Detach the toilet SEAT from the existing toilet and take it onto the porch.

2) Affix smallish blocks to the UNDERSIDE of that toilet seat that will keep the seat from sliding off the top of the bucket.

3) Set the detached toilet seat on top of the bucket and use.

Sue