On the chips, throw out all the characters after the last digit. Package info is not important until you find out what is available.
The TIL311 is not current production but they are all over eBay. You may need to take a chance and buy through them. They are a very nice display with built in latch and driver. I used a bunch of these back around '80 or so.
That blue LED ( LNG995PFBW) is just a blue LED. Read the datasheet for Vf and If and then drill down through the dozens of other blue LEDs until you find something close. You only care about the fact that it is through-hole and it would be ideal (but not required) that the forward voltage and forward current be similar. There is learning in reading datasheets and recalculating the series resistor to accommodate reality. Here's one that is in stock but I haven't checked the specs
https://www.digikey.com/product-detail/en/cree-inc/C5SMF-BJE-CR0U0451/C5SMF-BJE-CR0U0451-ND/4793773My guess is that a blue LED is a blue LED is a blue LED... Close enough for government work. Vf=3.4V, If=20mA OK, I did check the datasheet and the original has a Vf of 3.5V and If of 20 mA so, as I said, close enough!
It is an exercise to buy all of the parts for all of the experiments because many are either redundant, trivial or just 'make work'. Do the ones that provide real learning and blow off those that are obvious.
If you're diligent, I think you can find the parts somewhere.