The Best Answer
Squats, but if this is while using Occam`s, I wouldn`t use squats without a power rack and the pins set at the right height, or a spotter on either side.
*added* - While I was thinking more about this, it depends on what you have available to you. If you have a squat rack available, and it's okay to drop the weights, you could do front squats, and just dump the weight forward once you're true failure has hit(which would be you dropping down to a full squat after trying your best to get all the way up). However, this might be a bit dangerous if you drop the weight on your knees.
What do you have available to you? Heavy dumbbells and wrist wraps? Power rack? Knowing what you DO have access to would make it easier to say what you could try instead.
Yep, you didn't mention if you're doing these at a gym or at home. At home, we don't have a leg press either, so my boyfriend did 20 dumbbells squats holding 50lb dumbbells in each hand. At 5/5 cadence, it was really heavy on his fingers, and since I weigh about 100 lbs, I jumped on his shoulders and he did 10 more squats with me on his shoulders. Probably not exactly the best recommendation, but we both got a good laugh out of it regardless. So we're also is search of a good leg press alternative if anyone knows of any.