Wedding on two separate days

I agree with the other comments- have a family member or friend act as the officiant on the 2nd day just be sure to pick someone who is okay with speaking in front of a larger group of people

Your two weddings arw different as they are of different cultures. You choose to have ans Officiant for the Sunday wedding, you cqn let them know the signing is done and the civil weeding is just something you decided to have. If you feel an Officiant isn't needed for the Sunday wedding, avoid it all together and have someone from the family or a close friend to marry you

I agree with Hank, if you are legally getting married on Saturday, Sunday you don't need to spend money on Officiant you could have someone special to you say something that you wish they said Saturday and if you aren't writing your own vows on Saturday, that is something you both can do Sunday, especially if on both days you are having the same guests come to the second wedding this ways it's not a repeat of Saturdays event.

Are the guests the same for both ceremonies? If so, it might feel weird for them to see you do it twice.

If your religious ceremony is also the legal ceremony, then there's no point in doing a second ceremony other than it being for show. And if that's the case, you don't even need an officiant. Anyone can do it.