I take no credit for having 'invented' this, but it's so simple to do that it would be daft not to share. The acrylic sheets cost £3.50 from eBay (including the postage) and the bolts and wingnuts about the same from a local shop. It took a couple of minutes to put together and will save endless amounts of future faffing about with hand-squeezing, improvised weights and kitchen roll. Well worth the 'effort'.
2 x 6mm acrylic sheet, around A5 size (210x148mm)
4 x 8x100mm bolts with matching wingnuts (washers optional)
Drill four 8mm diameter holes in each corner of the acrylic sheets, around 20mm in from the edges. Put a washer on each bolt then put the bolts through the corner holes. Screw on the wingnuts. Done.
To use, simply put your tofu* between the sheets and lightly tighten up the wingnuts until it's held in position. Put the press on its edge on a plate and give the wingnuts a twist or two every minute or so until the tofu offers up a fair bit of resistance but doesn't split, then leave for another few minutes to drain completely.
*For extra-chewy / absorbent tofu, freeze it first then allow to defrost before pressing.