A garter bar makes quick work of turning your knitting to make purl stitches (and to hold stitches for various techniques). The trick for the LK150 is to find a garter bar created for the 6.5mm pitch These garter bars are rare
What is a Garter Bar?

Use this device to visually follow a drawing to shape garment pieces. For the LK150 the KnitRadar attaches with a cable to a row counter with a special port. The row counter then increments the KnitRadar row by row.

The KR10 and KR 11 knit Radars are no longer being made, but used devices can be found What is a Charting Device?

Even though the LK150 is not an electronic or punchcard machine, we can use DAK to create garment shapes and use the Interactive Knitting module as a Charting device. or create garment knitting instructions in a number of formats to follow.
What is DesignaKnit?

Buy Designaknit and cables from Knit it Now

At one time, there were "kits" that provided sections of the LK150 needlebeds so you could extend your machine by groups of 50 needles.

The cost of the "kits" became prohibitive and the US distributor no longer offers them.
However, if you can find a used LK150 at a reasonable price, you might consider breaking it apart and extending your machine so you can knit wider pieces.
Consider 200 or 250 stitches with one pass of the carriage!
Plus having 2 carriages can come in handy!
Extend an LK150

Easily knitting color blocks or multiple colors across the row with a single pass of the carriage is a time saver.
An intarsia carriage makes Intarsia (Picture Knitting) fast and easy. Buy an Intarsia Carriage from Knit it Now

A fairisle carriage makes stranded knitting or fairisle easy. Most metal bed machines allow you to knit 2 colors across the row with a single pass of the carriage. However the LK150 requires a separate carriage that is no longer available.
Fairisle can be worked by manually selecting needles and knitting colors with multiple passes of the carriage

This clever device makes it easier to select needles for 8 stitch repeats across the row without counting.
Needle Beetle