most suppliers of proofing software (like CGS, EFI, GMG,...) offer newspaper proofing substrate. Those are very newspaper like papers with usually a slight inkjet coating, so the ink doesn't bleed too much.
For the HP1050 series I've also come across separate roll holders, so you can directly mount butt rolls from newsprint presses.
One word of caution on newspaper proofing in general:
the quality of newsprint has dramatically improved (I don't know about the US, but over here in Europe they sometimes almost look like web printing with clean colors and crisp shadows). So I noticed that many inkjet proofing systems on newsprint or newsprint-like substrates are unable to reproduce what modern newsprint can achieve. Shadows and bright colors look duller on the proofer than on the final result.
The HP1050 seems the most common unit for newsprint proofing and because its ink type (dye for CMY and pigment for K) it was well suited for newsprint proofing, but stands no chance to achieve even 3/4 of current newspaper's gamut when loaded with butt rolls.
So when you work with newspapers you should check the profile you'd like to simulate (like SNAP / ISOnewspaper30, or for Europe: ISOnewspaper26v4) against your proofer gamut - tools like ColorThink can graphically display that. If your proofer has a smaller gamut than what you intend to simulate, then you know you'll have problems. In that case research a different paper for your proofer.
