Indoor is tough, since you dont say what bands you are trying to pick up. If you have a indoor tv antenna with a 75 ohm coax you could get an adapter for your scanner and try that. If you are trying to get a specific band, you should be able to find a 1/4 wave or 5/8 wave whip for your scanner which will work better than the helical duck that comes with them.
Where do you plan on putting the antenna? Indoor could mean many things. I have an antenna in the attic, so that would be an indoor antenna. What frequencies are you trying to receive? That will also affect your options.
What scanner? What antenna are you using? Monitoring Delaware county?