Cello bags can be heat sealed, as long as they are made from polypropylene or another compatible material. You can use a regular commercial sealer for this purpose. However, for the best results, you should consider utilising a specialised heat sealer.
If you’re sealing a cello bag, then it is likely that an impulse heat sealer will be enough to do the job. With something as large and unweildy as a cello bag, it’s likely that you’ll want complete control over the heat sealing process, making a hand-held heat sealer the most effective option.